it's the opening for sonic CD, one of the better games for the old Sega CD (the extention for the old Gennissis console) as I recal it was defanantly the coolest of the old side scroleing sonci cames in terms of feel and sound (I listened to the music from all the time frames of all the levels forever), the game I think is older than I think 9 years old, it came out before Sonic 3 I'm positive (sonic3 and the S&K expantion (the only expantion pack for a console I've ever heard of) was the best of the seres in terms of gameplay and fun)
if you'v never played it, it does feel a bit off, as rather than trying to get the chaios emralds you are after the time stones on some moon that Robotnik is also trying to get (duh) as you play the game you get many opertunitys to travle back and forth in time and the levels change acordingly, if you take out the right targets in the past then the future of that level will be diferent, there is a similar effect from gathering all the stones, this was one of my all time favorite games largly from the music in the levels (though there was a lot of extreemly cool graphics)
I recomend you get your emulators running and find your self a copy, though it would likely be a 600mb DL (so you'r not likely to find it)
the ending sequence(s) were also very cool
